Certain types of wheeled vehicles, especially those used for off-highway applications such as agriculture and construction, are designed to be steered in any one of several steering modes. Front-wheel-only steering is usually preferred when transporting the vehicle from place to place at higher speeds since it imparts a familiar steering characteristic not unlike that of an automobile. On the other hand, the availability of four-wheel-radial steering and crab steering can improve vehicle productivity.
This is so since the relatively large size of such vehicles and the small, often-obstructed spaces in which they are frequently operated make it difficult to perform certain tasks using only conventional front-wheel-only steering. Like front-wheel-only steering, four-wheel-radial steering provides a steering characteristic not radically dissimilar from that of an automobile. However, crab steering is somewhat unusual in that it causes the vehicle to move sideways simultaneously with any forward or reverse movement. Such unusual movement can be disconcerting to the vehicle operator unless the operator has deliberately selected such steering mode.
Further, operators of such vehicles are intent on maneuvering the vehicle implement, a bucket or plow for example, and must observe such implement almost continuously when the vehicle is in operation. Such operators are distracted by any need to view the steering selector assembly when selecting a different steering mode. Therefore, quick, accurate selection entirely by tactile sensing is highly preferred.
A type of steering mode selector assembly is shown in U.S. Pat. No. 4,175,638 (Christensen). The selector assembly shown therein has four positions, any one of which may be selected by movement of the assembly handle.
To move the handle between any two positions, the operator must first depress it to bring a notch into registry with a groove, then move the handle to the new position being selected and finally release it for retention in such position. Selection of a steering position in the foregoing manner may require the operator to look at the position of the steering handle while selection is being made. That is, quicker, more accurate selection of handle position will be accomplished if selection is other than entirely by tactile sensing. In the Christensen assembly, other steering characteristics may be employed in one of the aforementioned positions by rotational movement of the selector handle.
Yet another type of known steering mode selector apparatus uses a rotatable dial-type selector switch in conjunction with a rocker switch. To select a steering mode, the selector switch is first moved slightly to an unlocked position and then rotated until its pointer is in registry with a graphic indicator for the desired steering mode. With such apparatus, selection of a steering mode involves several hand movements and it is preferrable for the operator to view the rotatable selector switch to help assure that the pointer is set at the desired location.
U.S. Pat. No. 4,203,291 (Youngers) shows a type of selector embodied as a control mechanism for use with a hydraulic pump. To move the handle between any one of three positions on either side of neutral, it is first depressed to disengage pins from holes in the console and then moved to the new position while depressed. Releasing the handle causes the pins to engage other holes located at the new position. The mechanism also has a separate neutral lockout pin which must be disengaged whenever the handle is moved out of neutral. Other types of selector mechanisms are shown in U.S. Pat. Nos. 4,358,965 (Schroeder) and 3,184,989 (Rhodes).
A steering mode selector assembly which permits easy, quick selection of any one of three steering modes, which helps prevent inadvertent selection of a mode, which maintains the assembly in the selected mode and which can be readily operated using tactile sensing would be an important advance in the art.